1. Field of the Invention
The present invention relates to a method and a device for cleaning drums in the manufacture of photoconductor drums for use with image forming apparatus such as electrophotographic copying machines or the like. More particularly, this invention relates to a method and device for cleaning drums such as aluminum drums or the like, before applying a coating solvent containing a photoconductive substance to the outer circumferential surface of the drum in the manufacture of photoconductor drums having a photoconductive layer formed on the outer circumferential surface thereof.
2. Description of the Prior Art
A photoconductor drum used with an image forming apparatus such as an electrophotographic copying machine or the like is manufactured by coating the outer circumferential surface of an aluminum drum with a photoconductive substance to form a photoconductive layer thereon. Prior to the coating of the photoconductive substance, the aluminum drum is cleaned to remove metal powder, grease, and other foreign matter adhering the surface thereof, so that the photoconductive substance can be applied in a uniform thickness onto the outer circumferential surface thereof.
One known method of cleaning such an aluminum drum is to spray a cleaning fluid onto the outer circumferential surface of the aluminum drum. In this cleaning method, as shown in FIG. 2, a cleaning fluid is sprayed inwardly from nozzles 91 arranged in a circular configuration while an aluminum drum 10 is passed in rotating fashion through the inside space of the circular configuration toward which the cleaning fluid is sprayed. Thus, the cleaning fluid is sprayed onto the outer circumferential surface of the aluminum drum 10 to remove foreign matter adhering thereto. The cleaning fluid after being used for cleaning is collected in a storage tank 92 disposed beneath the nozzle 91. The cleaning fluid 93 in the storage tank 92 is pressurized by means of a pump 94 to feed to a filter 95 through which the cleaning fluid is filtered and cleaned and recirculated to the nozzle 91 for use for cleaning the aluminum drum 10. The cleaning fluid is thus effectively filtered and cleaned and recycled.
With the above drum cleaning method, to assure complete removal of metal powder, grease, and other foreign matter adhering to the outer circumferential surface of the aluminum drum 10, the cleaning fluid usually has to be sprayed through the nozzles 91 under a high pressure of 30-50 kg/cm.sup.2. Spraying the cleaning fluid through the nozzles 91 under a high pressure of about 50 kg/cm.sup.2 requires that the pressure loss of cleaning fluid must be decreased at the filter 95. Therefore, the filter 95 through which the cleaning fluid fed to the nozzle is passed through has a porous structure coarse enough to allow particles of 10 .mu.m or larger size to pass through; otherwise, spraying the cleaning fluid under such a high pressure would not be possible because of a decrease in the pressure applied to the cleaning fluid due to the presence of the filter 95. If the filter 95 has a porous structure coarse enough to allow particles of 10 .mu.m or smaller size to pass through is used, the pressure loss of cleaning fluid must be decreased at the filter 95, because the cleaning fluid cannot be sprayed under high pressure.
After cleaning the aluminum drum 10 used as a photoconductor drum for an image forming apparatus, the minimum allowable size of foreign particles to be deposited on the outer circumferential surface of the aluminum drum 10 is generally said to be about 0.2 .mu.m. When applying a coating solution containing a photoconductive substance on the cleaned drum surface, if any foreign particles larger than that size are left thereon, the coating solution cannot be applied uniformly where such particles are deposited, resulting in the formation of an image having missing portions on such areas. As described, when the filter 95 having a porous structure coarse enough to allow particles of 10 .mu.m or larger size to pass through is used, particles larger than the allowable size may not be trapped by the filter 95 and may be redeposited on the outer circumferential surface of the aluminum drum 10, thus resulting in a substantial drop in the cleaning effect even if the cleaning fluid is sprayed under high pressure.
In the case of spraying the cleaning filter under high pressure, if more than one filter having a coarse porous structure is used in parallel with each other, the cleaning fluid can be sprayed under high pressure to the drum surface while reducing the size of foreign particles allowed to pass through the filters. However, such arrangement requires the provision of a large number of filters, which not only impairs economy but could result in failure to completely remove particles in the cleaning fluid which are larger than the allowable size.